Transistion metal containing ceramic with metal nanoparticles

ABSTRACT

A transition metal-containing ceramic made by the process comprising the step of pyrolyzing an organometallic linear polymer containing at least one metallocenylene unit, at least one silyl or siloxyl unit, and at least one acetylene unit to form a ceramic; where the ceramic has a ceramic yield of at least about 75% by weight. A transition metal-containing ceramic made by the process comprising the steps of: forming an organometallic linear polymer containing at least one metallocenylene, at least one silyl or siloxyl unit, and at least one acetylene unit; crosslinking said linear polymer through the acetylene units, thereby forming a thermoset; and pyrolyzing said thermoset to form a ceramic; where the ceramic has a ceramic yield of at least about 75% by weight.

This application is a continuation-in-part application of pending U.S. patent application Ser. No. 08/818,193 filed on Mar. 14, 1997, now U.S. Pat. No. 6,495,483 issued on Dec. 17, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new class of transition metal containing linear polymers of varying molecular weight that are useful for conversion to high temperature thermosets and ceramics. These new materials have repeat units that contain alkynyl groups for cross-linking purposes along with organotransition metal complexes, silyl, siloxyl, boranyl, or di(silyl or siloxyl)carborane units. These novel linear polymers with the metal units in the backbone are soluble in most organic solvents and can be easily fabricated from the melt into shaped components, which enhance their importance for high temperature structural, magnetic, and microelectronic applications. Cross-linking of alkynyl groups is known to occur by either photochemical or thermal processes. The ceramics may also contain carbon nanotubes and/or metal nanoparticles.

2. Description of the Prior Art

The incorporation of transition metals into a polymer structure has long been seen as a good way of preparing materials with different properties from conventional carbon-based polymers. Small molecule transition metal complexes and solid state compounds possess an array of interesting high temperature, hardness, redox, magnetic, optical, electrical, and catalytic properties. In addition, the rich diversity of coordination numbers and geometries available for transition elements offer the possibility of accessing polymers with unusual conformational, mechanical, and morphological characteristics.

The development of polymers with transition metals in the main chain structure would be expected to provide access to processable, specialty materials with similarly attractive physical properties that would be of interest as pyrolytic precursors to metal-containing ceramics. Transition metal-based polymers might also function as processable precursors for making metal-containing ceramic films and fibers with high stability and desirable physical properties. Most transition metal-based polymers reported to date, however, do not contain units for conversion to a thermoset and thus afford low char yields at elevated temperatures.

Despite early synthetic problems of constructing macromolecular chains, researchers have now prepared a variety of metal-containing polymers with novel properties. Ferrocene-based polymers appear to be particularly promising as reported by Ian Manners in Chain Metals, Chemistry In Britain, January 1996, pp. 46-49. Because of ferrocene's ability to release and accept an electron reversibly, there is considerable interest in developing these materials as electrode mediators and in energy storage devices.

These mediators, for example, facilitate electron transfer between an enzyme such as glucose oxidase, where the redox active sites are buried in a protein sheath and an electrode. Ferrocene-based polymers have been successfully used as electron relays in electrochemical biosensors for measuring glucose levels. Scientists have also fabricated microelectrochemical devices such as diodes using ferrocene-based polymers.

Other studies have reported on the formation of Fe—Si—C materials from the pyrolysis of iron containing polymers. See, for example: (1) Tang, B. Z.; Petersen, R.; Foucher, D. A.; Lough, A.; Coombs, N.; Sodhi, R.; Manners, I. J Chem. Soc., Chem Commun. 1993, 523-525; (2) Peterson, R; Foucher, D. A.; Tang, B. Z.; Lough, A.; Raju, N. P.; Greedan, J. E.; Manners, I. Chem. Mater. 1995, 7, 2045-2053; and (3) Ungurenasu, C. Macromolecules 1996, 29, 7297-7298; (4) Hodson, A. G. W; Smith, R. A. Transition Metal Functionalized Polysilazanes as Precursors to Magnetic Ceramics, Faculty of Applied Sciences, University of the West of England, Bristol, BS16 1QY.

Spirocyclic [1]-ferrocenophanes have been reported to function as convenient cross-linking agents for poly(ferrocenes) via thermal ring-opening copolymerization reactions by MacLachlan, M. J.; Lough, A. J.; and Manners, I, in Macromolecules, 1996, 29, 8562-8564.

The use of ring-opening polymerization (ROP), a chain growth process, is reported by I. Manners in Polyhedron, Vol. 15, No. 24. pp 4311-4329, 1996 to allow access to a range of high molecular-weight polymers with skeletal transition metal atoms having novel properties.

Several poly(ferrocenylsilanes) have been synthesized and converted into ceramics upon heating to 1000° C. under inert conditions. See, for example, Pudelski, J. K.; Rulkens, R.; Foucher, D. A.; Lough A. J.; MacDonald, P. M. and Manners, I., Macromolecules, 1995, 28, 7301-7308. The ceramic yields by thermogravimetric analysis (TGA), however, were in the range of 17 to 63%.

Alternative transition metals such as ruthenium have also been reported as being incorporated into a metallocenophane structure by Nelson, J. A.; Lough, A. J., and Manners, I in “Synthesis and Ring-Opening Polymerization of Highly Strained, Ring-Titled[2]Ruthenocenophanes” Angew. Chem., Int. Ed. Engl. 1994, 33, 989-991 and in “Synthesis, Structures, and Polymerization Behavior of Di-silane-Bridged and Bis(disilane)-Bridged[2]Ruthenocenophanes” in Organometallics 1994, 13, 3703-3710. Novel ruthenium or iron containing tetraynes as precursors of mixed-metal oligomers are reported in Organometallics 1996, 15, 1530-1531. Mixed valence diferrocenylacetylene cation compounds have been reported in the Journal of the American Chemical Society, 96:21, 1974, pp. 6788-6789.

The synthesis and characterization of linear boron-silicon-diacetylene copolymers is reported by R. A. Sundar and T. M. Keller in Macromolecules 1996, 29, 3647-3650. Additionally, the efficient, “one-pot” synthesis of silylene-acetylene and disilylene-acetylene preceramic polymers from trichloroethylene is reported in the Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 28, 955-965 (1990).

Furthermore, the preparation and reactions of decachloroferrocene and decachlororuthenocene is disclosed in the Journal of the American Chemical Society, 95, 870-875 (1973). Symmetrically disubstituted ferrocenes are discussed in the Journal of Organometallic Chemistry, 27 (1971) pp. 241-249, as well as ferrocenyl-acetylene being disclosed in the J. Organometal. Chem., 6 (1966) pp. 173-180 and 399-411. Ferrocenyl- and 2-thienylarylacetylenes are reported by M. D. Rausch; A. Siegal and L. P. Kelmann in J. of Org. Chem. 1966, Vol. 31 p. 2703-2704.

Ferrocenyl ethylene and acetylene derivatives are also reported by P. L. Pauson and W. E. Watts in J. Chem. Soc. 1963, 2990-2996. Studies on the reactions of ferrocenylphenylacetylene and diferrocenyl-acetylene are reported in the Journal of Organometallic Chemistry, 149 (1978) 245-264. The chemistry of π-bridged analogues of biferrocene and biferrocenylene is discussed in the Journal of Organic Chemistry, Vol. 41, No. 16, 1976, 2700-2704. The synthesis of 1′,6′-bis(ethynyl)-biferrocene and metal complexes referring to non-linear optics is presented in Polyhedron, Vol. 14, No. 19, pp. 2759-2766 (1995).

In addition to these documents discussing the various compounds and polymers, the catalytic graphitization by iron of isotropic carbon is reported in Carbon, Vol. 21, No. 1, pp. 81-87, 1983. Preceramic polymer routes to silicon carbide are disclosed by Richard M. Laine in Chem. Mater. 1993, 5, 260-279; and the comprehensive chemistry of polycarbosilanes, polysilazanes and polycarbosilazanes as precursors of ceramics is thoroughly reported in Chem. Rev., 1995, 95, 1443-1477.

U.S. Pat. Nos. 4,800,221 and 4,806,612 also respectively disclose silicon carbide preceramic polymers and preceramic acetylenic polysilanes, which may be converted into ceramic materials.

U.S. Pat. Nos. 5,241,029 and 5,457,074 disclose diorganosilacetylene and diorganosilvinylene polymers that can be thermally converted into silicon carbide ceramic materials.

U.S. Pat. No. 4,851,491 discloses polyorganoborosilane ceramic polymers, which are useful to generate high temperature ceramic materials upon thermal degradation. U.S. Pat. No. 4,946,919 also relates to boron-containing ceramics formed from organoboron preceramic polymers, which are carboralated acetylenic polymers.

U.S. Pat. Nos. 5,272,237; 5,292,779; 5,348,917; 5,483,017 disclose carborane-(siloxane or silane)-unsaturated hydrocarbon based polymers reported to be useful for making high temperature oxidatively stable thermosets and/or ceramics.

U.S. Pat. No. 5,552,505 discloses copolymers formed from aromatic acetylenic monomers or prepolymers formed therefrom and carborane-(siloxane or silane)-unsaturated hydrocarbon polymers reportedly useful to form articles, adhesives, matrix materials, or coatings, or which may be pyrolyzed to form carbon-ceramic composites. Each of the documents cited herein contains valuable information and each is incorporated herein by reference in its entirety and for all purposes.

Most of the carborane-siloxane and/or carborane-silane polymers made by others have elastomeric properties rather than properties of more rigid polymeric products like thermosetting polymers or ceramics. There is a need for polymers that behave less like elastomeric polymers and more like thermosets and which, upon pyrolysis, form ceramics.

U.S. patent application Ser. Nos. 10/216,469 to Keller et al. and 10/216,470 to Keller et al., incorporated herein by reference, disclose the formation of carbon nanotubes and metal nanoparticles from the pyrolysis of compositions containing metallocene, ethynyl groups, and/or metal ethynyl complexes. These complexes did not contain any silicon. Upon heating, the ethynyl groups crosslinked to form a thermoset. Further heating caused the metal-containing groups to degrade releasing elemental metal. This process can catalyze the formation of carbon nanotubes in the bulk material. The metal can also coalesce into nanoparticles.

There is, therefore, a need for oxidatively stable materials having thermosetting properties for making rigid components therefrom which withstand high temperatures and which have high strength and high hardness properties and/or which optionally may have magnetic properties.

Furthermore, there is a need for transition metal-based polymers that contain units for conversion to thermosets and which afford high char yields at elevated temperatures. There is also a need for such polymers which would be useful precursors to novel materials unavailable from other sources, and which may exhibit unique nonlinear optical (NLO) properties.

There is a further need for materials containing silicon and carbon nanotubes or metal nanoparticles in the bulk material.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide polymers having backbones incorporated with organotransition metals complexes along with silicon, acetylenic, and/or boron units which are useful as precursors to novel materials unavailable from other sources.

It is another object of the present invention to provide polymers having backbones incorporated with organotransition metal complexes along with silicon, acetylenic, and/or boron units which can be readily converted into high temperature thermosets.

It is another object of the present invention to provide polymers having backbones incorporating organotransition metal complexes along with silicon, acetylenic, and/or boron units which can readily be converted into high temperature materials which exhibit high strength properties, high hardness values, and electrical and/or magnetic properties.

It is yet another object of the present invention to provide transition metal based polymers that contain inorganic units and units for conversion to thermoset polymers and which afford high char yields at elevated temperatures.

It is still another object of the present invention to permit the formulation of ceramics containing a variable and controllable amount of metal and various cluster sizes.

It is still another object of the present invention to provide transition metal based ceramics that contain inorganic units and carbon nanotubes and/or metal nanoparticles.

These and other objects of the invention may be accomplished by a transition metal-containing ceramic made by the process comprising the step of pyrolyzing an organometallic linear polymer containing at least one metallocenylene unit, at least one silyl or siloxyl unit, and at least one acetylene unit to form a ceramic; where the ceramic has a ceramic yield of at least about 75% by weight.

The invention further comprises a transition metal-containing ceramic made by the process comprising the steps of: forming an organometallic linear polymer containing at least one metallocenylene, at least one silyl or siloxyl unit, and at least one acetylene unit; crosslinking said linear polymer through the acetylene units, thereby forming a thermoset; and pyrolyzing said thermoset to form a ceramic; where the ceramic has a ceramic yield of at least about 75% by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic depiction of the thermal stability of poly(ferrocene-methylsilane-diacetylene).

FIG. 2 is a thermogravimetric analysis (TGA) of dimethylsilylene-ferrocenylene-diacetylene polymer under N₂ (A) and the resulting char in air (B).

FIG. 3 is a thermogravimetric analysis (TGA) of tetramethydisiloxyl-carborane-ferrocenylene-diacetylene polymer under N₂ (A) and the resulting char in air (B).

FIG. 4 is the FTIR(KBr) spectra of ferrocenylene-carborane-siloxyl diacetylene (polymer II (A)) and thermoset (B) obtained by heat treatment of the polymer to 450° C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description of the invention is provided to aid those skilled in the art in practicing the present invention. However, it should not be construed to unduly limit the present invention. Variations and modifications in the disclosed embodiments may be made by those of ordinary skill in the art without departing from the scope of the present inventive discovery.

This invention discloses a new class of novel metallocene polymers containing acetylenic and inorganic units; a new class of novel thermosetting polymers made therefrom; and a new class of novel ceramics made from these. Scheme 1 (below) illustrates the synthesis of these novel materials according to the present invention.

The invention can be performed by either crosslinking a linear polymer, followed by pyrolysis to a ceramic, or by pyrolyzing the linear polymer. Suitable linear polymers include, but are not limited to, the following general composition:

where x, z, w, y, and a are greater than or equal to one; R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ may be the same or different and wherein each equal H, unsubstituted or substituted hydrocarbon moieties, unsubstituted or substituted alkyl or arylamino moieties; unsubstituted or substituted alkyl or aryl phosphino moieties; halogen; M=Fe, Ru, Os, or a combination thereof; and E is

or R¹³B; where f, p, q, and t are greater than or equal to zero; g and h are greater than or equal to one; h is greater than or equal to one; s is greater than or equal to zero and is greater than or equal to one when q is greater than or equal to one; k is an integer from 3 to 16; R⁹, R¹⁰, R¹¹, R¹² may be the same or different and wherein each is H, unsubstituted hydrocarbon moieties or substituted hydrocarbon moieties; and R¹³ is unsubstituted or substituted hydrocarbon moieties.

As suggested above, R¹ through R¹³ may each be one of any monovalent organic group, or, in the case of R¹-R¹², may be hydrogen. R¹ through R¹³ may be aromatic, aliphatic, or include both aliphatic and aromatic moieties. R¹ through R¹³ may be saturated or include unsaturation. In all cases, R¹ through R¹³ may be halo-substituted. The carborane may be ortho, meta, or para.

Also, throughout the specification and claims, it should be understood that the value of E, and its associated variables, may differ at each occurrence of E within the polymer, within the definitions provided for E and its associated variables. Thus, throughout the specification and claims, it should be understood that E and the variables included therein do not represent singular and constant values throughout the polymer. Instead, E and the variables included therein represent values that may vary, within the proscribed limits, throughout the polymer.

Typical groups for R⁹-R¹² are, for example, hydrogen, methyl, ethyl, n-propyl, isopropyl, phenyl, and tolyl. More often, R⁹-R¹² are hydrogen, methyl, or ethyl. Most often R⁹-R¹² are hydrogen or methyl.

Typically, R¹³ is methyl, ethyl, n-propyl, isopropyl, and the like, or phenyl, tolyl, and the like; most typically, R¹³ is methyl, ethyl, or phenyl.

A typical “E” component may have k=3 to 12; a more typical “E” component having k=5 to 10; the even more typical “E” component having k=8 to 10; and the most typical “E” component having k=10.

Typical ranges for “f” include 0 to 10; more typically 0 to 6; and most typically from 0 to 2.

Typical ranges for “g” include 1 to 10; more typically 1 to 6; and most typically from 1 to 2.

Typical ranges for “h” include 1 to 50; more typically 1 to 20; and most typically from 1 to 5.

Typical ranges for “p” include 0 to 50; more typically 0 to 20; and most typically from 0 to 5.

Typical ranges for “q” include 0 to 10 more typically 0 to 4; and most typically from 0 to 2.

Typical ranges for “s” include 0 to 10; more typically 1 to 6; and most typically from 1 to 2.

Typical ranges for “t” include 0 to 10; more typically 0 to 6; and most typically from 0 to 2.

Typical ranges for “w” in these organometallic polymers, thermosets, and ceramics are from 1 to 100; more typically from 1 to 50; more often typically from 1 to 20; even more often from 1 to 10; and most often 1 to 3.

Typical ranges for “y” in these organometallic polymers, thermosets, are from 1 to 100; more typically from 1 to 50; more often from 1 to 20; even more often 1 to 10; and most often 1 to 3.

Typical ranges for “z” in these organometallic polymers, thermosets, and ceramics are from 1 to 100; more typically from 1 to 80; more often from 1 to 50; even more often 1 to 30; and most often 1 to 20.

Typical “M” components of these novel organometallic polymers, thermosets and ceramics include transition metals; more typically being Fe, Ru, Os or combinations thereof; most typically being Fe, Ru or combinations thereof; most preferred being Fe. Different amounts of iron can be added to these polymers, thermosets, and ceramics depending on the additive compounds or combination of compounds, for example, ferrocene, biferrocene, triferrocene, and the like may be incorporated. Typically “a” in these polymers, thermosets and ceramics may range from 1 to 20; more typically being from 1 to 10; more often being from 1 to 8; even more often being from 1 to 5; most often being from 1 to 3.

It should be understood that the general formula for the polymers describes both random and block copolymers. Throughout the specification and the claims that follow, the general polymer formula provided above will be used to represent a polymer having the structural elements shown, independent of the nature of the terminal groups. It should be further understood that a group described as “substituted” may be, for example, halo or haloalkyl substituted, unless otherwise explicitly stated.

The following general reaction represented in Scheme 1 illustrates the synthesis of the metallocene polymers containing acetylenic and inorganic units; the formation of thermosets therefrom; and the ultimate formation of the novel ceramics. In Scheme 1, X is a leaving group, such as a halogen, tosylate, and trifluoromethane sulfonate. Where EX₂ in Scheme 1 is a mixture of various compounds in which E and X meet the above-provided definitions, E and its associated variables will have different values at different occurrences within the polymer. Of course, each E, and its associated variable within the polymer, will meet the definitions provided for them in the present application.

All variables are as described above. Throughout the specification and claims, it should be understood that the structure

represents a complex structure consisting of a plurality of cross-linked acetylenic moieties. The structure shown is not intended to be representative of the actual cross-links existing within that structure. In reality, the cross-linked acetylenic moiety may include several different cross-linking structures such as those shown below.

The conversion of the linear polymers to the cross-linked polymers is accomplished by either exposing the linear polymer to heat or light. Prior to cross-linking, fibers, foams (or other porous materials) and/or particles, etc., made from, e.g., glass, carbon, silicon carbide, and boron carbide, or metals, can be placed in the material to allow the formation of a composite material upon cross-linking. The extent of thermal conversion of the carbon-to-carbon triple bonds in the linear metallocene polymers to form the thermosetting polymers is dependent on both the curing temperature and the curing time. The heating of the linear polymers is carried out over a curing temperature range sufficient for the reaction of the carbon-to-carbon triple bonds of the individual linear polymers to occur resulting in the formation of a mass of cross-linked polymers. The heating of the linear polymers is carried out over a curing time sufficient for the reaction of the carbon-to-carbon triple bonds of the individual linear polymers to occur resulting in the formation of the cross-linked polymers.

In general, the curing time is inversely related to the curing temperature. The typical temperature range, the more typical temperature range, the most typical temperature range and the preferred temperature range for the thermal conversion of linear polymers to the cross-linked thermoset polymers are, typically, 150-500° C., 200-400° C., 225-375° C., and 250-350° C., respectively. The typical curing time, the more typical curing time, and the most typical curing time for the thermal conversion of linear polymers to the cross-linked thermoset polymers are 1-48 hours, 2-24 hours, and 8-12 hours, respectively.

The photo cross-linking process, of converting the carbon-to-carbon triple bonds of the linear polymers into unsaturated cross-linked moieties necessary for forming the thermosetting polymers, is dependent on both the exposure time and the intensity of the light used during the photo cross-linking process. Ultraviolet (UV) light is the most preferred wavelength of light used during the photo-cross-linking process.

The exposure time of the linear polymers to the UV light is inversely related to the intensity of the UV light used. The exposure time to the UV or to other light used is that time which is sufficient for the carbon-to-carbon triple bonds of the linear polymers to be cross-linked to form the thermosetting polymers. The intensity of the light used is that intensity which is sufficient for the carbon-to-carbon triple bonds of the linear polymers to be cross-linked to form the thermoset polymers.

Furthermore, the wavelength of the light used is not limited to the UV range. The wavelength of light used is that wavelength which is sufficient for the carbon-to-carbon triple bonds of the linear copolymers to be cross-linked to from the thermoset copolymers. The typical exposure time, the more typical exposure time, and the most typical exposure time are 1-100 hours, 24-36 hours, and 12-24 hours, respectively. Curing times of 4-8 hours are also relatively common. Examples of the conversion for linear copolymers to the cross-linked thermosets are given infra.

General Scheme 2 also illustrates, generally, the synthesis of these novel organometallic polymers, which can be converted to thermosets and ultimately formed into ceramics.

As can be noted from the synthesis of these hybrid copolymers the silyl, siloxyl, carboranedisiloxyl, or boranyl groups are separated randomly by a metallocenyl group and/or an acetylenic group. The synthesis of these copolymers is straightforward and high-yielding. For example, the synthesis of the copolymers made according to the examples was performed using the method outlined in Scheme 2. Hexachlorobutadiene is reacted with four equivalents of n-butyllithium affording dilithiobutadiyne. Treatment of dilithiobutadiyne with 2 molar equivalents of dimethyldichlorosilane followed by addition of dilithioferrocene yields the linear copolymer after aqueous workup or quenching with trimethylsilylchloride followed by aqueous workup.

The setup of this reaction makes it simple to change the chemical make-up of these copolymers by varying the molar ratios of dilithiometallocene and dilithiobutadiyne such that their total number of moles is equivalent to the number of moles of the silyl, siloxyl, carboranesiloxyl and boranyl dihalides, ditosylates, and bis(trifluoromethane sulfonates) used. In addition, substituting trichloroethylene for hexachlorobutadiene leads to a copolymer with only one carbon—carbon triple bond in the repeat unit. Thus, by forming the appropriate alkynyl salt, the length of the alkynyl moiety, which is incorporated into the copolymer, can be controlled. The synthesis of these salts is disclosed in U.S. Pat. No. 5,483,017, which, as noted previously, is herein incorporated by reference in its entirety for all purposes.

Typically, the value of x in the general formula of those novel organometallic copolymers can be varied from 1 to 10. Acetylenic derivatives having the general formula H(C≡C)_(n)H can be readily converted into the dilithio salts by reacting with n-butyllithium. The respective dilithio salts, with values of x varying from 1 to 10, can then be incorporated into the backbone of the copolymers as shown. The value of x, typically from 1 to 10; more typically from 1 to 8; most typically from 1 to 5; more often from 1 to 3; and most often from 1 to 2.

Substituting 1,3-dichlorotetramethyldisiloxane for dimethyldichlorosilane would give a disiloxyl spacer in the copolymer instead of a silyl spacer.

Another important way to modify the chemical composition of these copolymers, thermosets, and ceramics is to change the identity of the metallocenylene unit. For instance, use of dilithioruthenocene in place of dilithioferrocene would give a copolymer containing ruthenium in the repeat unit. Mixed metal systems can be obtained by substituting a partial molar quantity of one dilithiometallocene for another. For example, the reaction of one molar equivalent of dilithioferrocene and one equivalent of dilithioruthenocene with two equivalents of dilithiobutadiyne and four equivalents of dimethyldichlorosilane would yield a copolymer containing both iron and ruthenium in the repeat unit. Substituted metallocenes may also be incorporated into the copolymer where the substituent is compatible with dilithiation to form the substituted dilithiometallocene. Thus, use of dilithiobutylferrocene and dilithiobutadiyne to react with dimethyldichlorosilane would give a copolymer containing butylferrocenyl groups in the repeat unit. Therefore, it is possible to tailor a copolymer according to specific needs.

These linear copolymers can readily be converted to high temperature thermosets upon polymerization through the acetylenic units at temperatures above 150° C. For example, the linear copolymer, Polymer I, contains acetylenic units through which cross-linking to a network (thermoset) polymer can occur under thermal conditions. Thermal treatment of Polymer I to 1000° C. under inert conditions affords a char yield of 75-90%. In essence, the organometallic linear copolymers of this invention may exhibit unique nonlinear optical (NLO) properties and serve as precursors to both thermosets and ceramics, which exhibit unique properties. As noted above, polymers containing ruthenocene and other organotransition metal complexes can also be synthesized in the same manner as described.

Upon heat treatment and conversion to a ceramic material, the overall composition will be different than precursor compounds and polymers that do not contain the acetylenic units. Due to the acetylenic unit, more carbon may be available for conversion within the ceramic system. Without the acetylenic unit, the only source of carbon would be from the five membered rings of the metallocene moiety. The methyl groups on the silicon atoms would be expected to break-off and volatilize from the system and not contribute to carbon remaining in the ceramic composition.

The thermoset precursor materials of the invention can be a shaped (solid, film, or fiber) composition. The fact that the units of initial linear polymer are linked together from polymerization of the acetylenic moieties is responsible for the high char yield or retention of weight upon thermal treatment of precursor thermoset to elevated temperatures. The char yield may be about 75% or higher. When ceramics powders are formed from a composition of linear polymers without acetylene groups, no thermoset is formed and the thermal breakage of bonds results in the evolution of these fragments as volatiles and explains the low char yield. The ceramic may be at least 55% total carbon and silicon by weight.

The ceramic may also comprise carbon nanotubes and/or metal nanoparticles. During heating the metallocenyl group may decompose, releasing elemental metal. The elemental metal may coalesce into metal nanoparticles. Metal nanoparticles may begin to form at about 350° C. The size of the metal nanoparticles may depend on the mobility of the metal atoms, which in turn may depend on the viscosity of the composition and the heating conditions.

Metallocenyl groups may tend to degrade at temperatures such as about 300° C. The degradation temperature may affect the size of the metal nanoparticles. If degradation occurs after crosslinking is complete and the composition is a solid thermoset, it may reduce the mobility of the metal atoms and form smaller nanoparticles.

A metallocenyl group may degrade before crosslinking is complete while the composition has low viscosity. The metal atoms may have higher mobility in this low viscosity composition and form larger nanoparticles. However, if the heating is fast enough, a thermoset may form before the metal nanoparticles have time to grow in size.

Carbonization may occur when the heating is continued. This may cause the formation of carbon nanotubes and/or carbon nanoparticles. These processes may occur at or above a temperature of from about 500° C. to about 1600° C. The amount of carbon nanotubes and carbon nanoparticles produced can be affected by the reactants, the heating conditions, and the properties of the metal nanoparticles.

Higher temperatures and/or longer heating times may be required to form carbon nanotubes than to form carbon nanoparticles. When the heating is sufficient, the metal nanoparticles may catalyze the assembly of carbon nanoparticles into carbon nanotubes. Carbon nanotubes may also grow from free carbon or from the organic compound.

The carbon nanotubes may be single-walled nanotubes (SWNT) or multi-walled nanotubes (MWNT. The diameter of the tubes may be controlled by the size of the metal nanoparticles. Larger metal nanoparticles may result in larger diameter carbon nanotubes, such as MWNT's.

The carbon nanotube composition may have magnetic properties that are caused by the metal, the carbon nanotubes, or both. The carbon nanotube composition may be a magnetic semiconductor. In some cases, metal may react with the carbon nanotubes, the carbon nanoparticles, or the carbon domain.

The presence of carbon nanotubes can be confirmed by Raman spectroscopy (FIGS. 1 and 2), x-ray diffraction (FIG. 3), HRTEM, and HRSEM. The following diffraction peaks are observed in a x-ray diffraction scan taken with CuKα radiation.

2θ hkl d (Å) 25.94 111 3.4347 42.994 220 2.1036 53.335 222 1.7940 78.798 422 1.2145

The above diffraction peaks in a x-ray scan are known in the art to be the fingerprints for the presence of carbon nanotubes. The diameters of the carbon nanotubes can be estimated from the FWHM of the peaks and the Scherrar equation. From the diameters obtained, one can deduce whether the carbon nanotubes are single-walled or multi-walled.

EXAMPLES

All reactions were carried out under inert atmosphere using standard Schlenk techniques. Tetrahydrofuran (THF) was distilled from sodium/benzophenone under N₂ immediately prior to use. Ferrocene was purchased from Strem Chemical and sublimed prior to use. (LiC₅H₄)₂Fe tmeda was prepared according to literature procedures (i.e., Bishop, J. J.; Davison, A.; Katcher, M. L.; Lichtenberg, D. W.; Merrill, R. E.; Smart, J. C. J. Organomet Chem. 1971, 27, 241). Hexachlorobutadiene was purchased from Aldrich Chemical Co. and distilled prior to use. N,N,N′,N′-tetramethylethylenediamine-(tmeda) and n-BuLi (2.5 M in hexanes) were purchased from Aldrich Chemical Co. and used as received. Dilithiobutadiyne was prepared according to literature procedures (Ijadi-Maghsooke, S.; Barton, T. J. Macromolecules 1990, 23, 4485; and, Ijadi-Maghsooke, S.; Pang, Y.; Barton, T. J. J. Polym. Sci., Part A: Polym. Chem. 1990, 28, 955). Dichlorodimethylsilane and dichloromethylsilane were purchased from United Chemical Technologies or Strem Chemical and distilled from Mg chips under N₂ immediately prior to use. The 1,7-bis-(chlorotetramethyldisiloxyl)-m-carborane was purchased from Dexsil Corp. and used as received. All other chemicals were of reagent grade.

Thermogravimetric analyses (TGA) were performed on a TA Instruments SDT 2960 Simultaneous DTA-TGA thermogravimetric analyzer. Differential scanning calorimetry (DSC) experiments were performed on a DuPont 910 instrument. All thermal measurements were carried out at a heating rate of 10° C./min and a gas flow rate of 60 mL/min. Gel permeation chromatography (GPC) data were collected using a Hewlett-Packard Series 1050 pump and two Altex u-sphereogel columns (size 10³ and 10⁴ Å, respectively) connected in series. All GPC values were referenced to polystyrene standards. Infrared spectra were recorded using a Nicolet Magna 750 FTIR spectrometer. ¹H and ¹³C NMR spectra were recorded on a Bruker AC-300 NMR spectrometer in CDCl₃. Elemental analyses were performed by E&R Microanalytical Laboratory, Corona, N.Y.

The new ferrocenylene-silylene/siloxyl-diacetylene linear copolymers, Polymers I and II, were also prepared as shown in general Scheme 2 (supra).

Dilithiobutadiyne was generated in situ by reacting hexachlorobutadiene with four equivalents of n-butyllithium at −78° C. The reaction of dilithiobutadiyne with two equivalents of either dimethyldichlorosilane or 1,7-bis(chlorotetramethyl)-m-carborane at 0° C. in THF was followed by treatment with one equivalent of dilithioferrocene.tmeda. After work-up, the copolymers were obtained as tacky solids in 83-86% yield.

The infrared spectrum (NaCl) of Polymer I showed absorption bands at 3087, 2959, 2066, 1251, 1166, 1036, and 804 cm⁻¹. The bands at 3087, 1251, and 1166 cm⁻¹ are assigned to the 1,1′-ferrocenylene group. The absorption at 2066 cm⁻¹ is attributed to the butadiyne group. The bands at 2959 and 804 cm⁻¹ are assigned to the C—H and Si—C stretches of the dimethylsilylene groups, respectively. The infrared spectrum (KBr) of Polymer II was similar to that of Polymer I with an additional prominent absorption at 2596 cm⁻¹ (νB—H) verifying the presence of the carborane group. The butadiyne stretch appears at 2170 cm⁻¹. Bands at 2962, 1260, and 1075 cm⁻¹ are assigned to C—H, Si—C, and Si—O bonds of the tetramethyldisiloxyl linkages, respectively. A band at 3093 cm⁻¹ is attributed to the C—H stretch of the 1,1′-ferrocenylene groups (FIG. 4).

The ¹H NMR (300 MHz, CDCl₃) spectrum of Polymer I showed resonances at 0.2 ppm and between 4.5 and 5.5 ppm assigned to the methyl groups on the dimethylsilylene groups and cyclopentadienyl protons of the 1,1′-ferrocenylene linkages, respectively. The ¹³C{¹[H} NMR (75 MHz, CDCl₃) spectrum of Polymer I showed resonances at −0.44 and −0.20 ppm assigned to the methyl carbons of the dimethylsilylene groups. The resonances for the 1,1′-ferrocenylene carbons were observed at 73.56, 72.40, and 67.81 ppm.

The ¹H NMR (300 MHz, CDCl₃) spectrum of Polymer II showed resonances at 0.34, 0.27, 0.22, and 0.10 ppm for the siloxyl methyl groups. The 1.1′-ferrocenylene proton resonances appeared at 4.25 and 4.05 (major peaks) with smaller peaks of approximately equal intensity at 4.35, 4.30, 4.16, and 4.11 ppm. The B—H protons appear as a series of broad signals between 1.0 and 3.5 ppm. The ¹³C{¹H}NMR (75 MHz, CDCl₃) spectrum of Polymer II showed the siloxyl methyl groups at 0.62, 0.55, 0.48 and 0.30 ppm, the 1,1′-ferrocenylene carbon resonances at 72.97 (minor), 72.83, 71.67, 71.60 (minor), and 71.12 ppm and the carboranyl carbon shifts at 68.31 an 67.90 (minor peak) ppm. The diacetylenic carbons appear as two small singlets at 87.0 and 84.6 ppm.

Thermogravimetric analysis (TGA) of Polymer I and II showed that these materials exhibit high thermal stabilities. Pyrolysis of Polymer I to 1000° C. (10° C./min, under N₂) gave 77% weight retention (FIG. 2). The ceramic yield observed for Polymer I can be compared to that reported for poly(dimethylsilylene-1,1′-ferrocenylene), which showed a weight retention of 36% at 1000° C. See: (a) Tang, B.-Z.; Petersen, R.; Foucher, D. A.; Lough, A.; Coombs, N.; Sodhi, R.; Manners, I. J Chem. Soc. Chem Commun. 1993, 523; (b) Petersen, R.; Foucher, D. A.; Tang, B.-Z.; Lough, A.; Raju, N. P.; Greedan, J. E.; Manners, I. Chem. Mater. 1995, 7, 2045. This difference is attributed to the formation of a cross-link through the diacetylene units prior to pyrolysis (vide infra), which significantly reduces weight loss due to depolymerization.

Heat treatment of Polymer II to 350° C. under inert atmosphere results in the formation of a black, somewhat more elastomeric than usual thermoset with 98% weight retention. A small amount of shrinkage was observed during the formation of the thermoset. The elastomeric nature of this thermoset is most likely due to the incorporation of the longer carboranyl unit into the copolymer. This contrasts to the hard, tough thermosets obtained from siloxyl-diacetylene polymers such as poly(tetramethyldisiloxyldiacetylene) reported by Son, D. Y.; Keller, T. N. J Polym Sci: Part A: Polym. Chem.: 1995, 33, 2969. Further heating of the thermoset to 1000° C. under N₂ affords a hard black, ferromagnetic ceramic in 78% ceramic yield. (FIG. 3). The ceramic chars obtained from pyrolysis of Polymers I and II to 1000° C. under N₂ were found to contain 16.6 and 4.89% iron, respectively, by elemental analysis. The elemental analysis of the chars from the pyrolysis of Polymers I and II to 1000° C. under N₂ respectively being: C, 56.8; H, 0.40; Si, 18.2; Fe, 16.6 and C, 35.7; H, 0.00; B, 20.25; Si, 21.7; Fe, 4.89. The elemental analysis of char obtained from heat treatment of Polymer II to 1500° C. gave: C, 35.67; H, 0.0; Si, 20.20; B, 20.44; Fe, 4.87.

Pyrolysis of the ceramic char obtained from Polymer I to 1000° C. (10° C./min) in air resulted in a weight retention of 55% at 750° C. As the temperature was increased, the sample slowly gained weight to yield a final weight retention of 60% at 1000° C. (FIG. 2). The observed weight gain is tentatively attributed to oxidation of the iron.

The ceramic chars obtained from Polymer II showed excellent oxidative stability with essentially 100% weight retention to 1000° C. in air (FIG. 3). The sample appears to maintain its magnetic character after such treatment. The excellent oxidative stability of Polymer II compared to that of Polymer I is attributed to the presence of the carborane groups in the copolymer backbone. High oxidative stabilities have been observed with related carborane containing polymers. See: Henderson, L. J.; Keller, T. M. Macromolecules 1994, 27, 1660, which is incorporated herein by reference.

Previous thermal (TGA) studies on 1,1′-ferrocenylene-siloxyl copolymer have shown these materials to have weight retentions of only 40-50% at 700° C. (10° C./min, N₂). (See: Patterson, W. J.; McManus, S. P.; Pittman, Jr. C. U., J. Polym. Sci., Polym. Chem. Ed. 1974, 12, 837, incorporated herein by reference.) The relatively high weight retention observed for Polymer II is attributed to prepyrolysis cross-linking of the diacetylene units. TGA of Polymer II to 1500° C. (10° C./min, N₂) revealed a second decomposition process beginning at 1350° C. and a final weight retention of 74%. Elemental analysis showed the latter material to be essentially identical in composition to samples that were prepared at 1000° C.

Differential scanning calorimetry (DSC) studies of Polymer I and II showed broad, strong exotherms with peak maxima from about 300° C. to 380° C. These exotherms are attributed to the thermal reaction (cross-linking) of the diacetylene groups. This latter assignment is supported by experiments on samples of Polymers I and II heated to 450° C., which showed the disappearance of the exotherm in the DSC trace and loss of the diacetylene absorption (2069 cm⁻¹) in the infrared spectrum.

Example 1

Synthesis of Polymer I—In a typical experiment, a solution of THF (10 ml) and n-BuLi (10.2 ml of 2.5 M, 25.5 mmol) at −78° C. was treated dropwise with hexachlorobutadiene (10 ml, 6.38 mmol) over 10 minutes. The reaction mixture was stirred at ambient temperature for 3 hours to afford dilithiobutadiyne. The resulting dark grey slurry was transferred via cannula to a flask containing dimethyldichlorosilane, Me₂SiCl₂ (1.55 ml, 12.78 mmol) in THF (5 ml) at 0° C. The solution was stirred for thirty minutes at room temperature then cooled in an ice bath and treated with a slurry of dilithioferrocene.tmeda, (2.0 g, 6.37 mmol) in 10 ml of THF. The resulting dark brown solution was stirred for one hour at room temperature and an infrared spectrum (NaCl) taken.

The IR spectrum of the crude reaction mixture showed a small peak at 2140 cm⁻¹ (terminal diacetylene groups). Several drops of Me₂SiCl₂ were added via syringe and the solution stirred for 20 minutes. The infrared spectrum was remeasured and additional drops of Me₂SiCl₂ were added if required. After the terminal butadiyne groups were no longer observed in the infrared spectrum, the solution was quenched with ice cold saturated NH₄Cl_((aq)) and purified by aqueous workup and extraction with diethyl ether. The Et₂O extracts were dried over MgSO₄, filtered, and the solvent removed leaving a viscous brown oil. Drying in vacuo at 50° C. for 8 hours gave a brown solid, which was soluble in THF, ether, and acetone but poorly soluble in hexane. Yield: 1.89 g(86%).

Example 2

Synthesis of Polymer II—A solution of THF (10 mL) and n-BuLi (10.2 mL of 2.5M) in a 250 mL Schlenk flask was cooled to −78° C. The solution was treated with hexachlorobutadiene (1.0 mL, 6.38 mmol) dropwise over a period of 10 minutes. The cold bath was removed and the solution was stirred at room temperature giving a grey-brown slurry. After stirring for 2 hours at room temperature, the slurry of dilithiobutadiyne was transferred via cannula to a flask containing a THF solution (10 mL) of 1,7-bis(chlorotetramethyldisiloxyl)-m-carborane (6.10 g, 12.77 mmol) at 0° C. The resulting mixture was stirred at room temperature for 30 minutes giving a brown solution. The solution was cooled to 0° C. and treated with a slurry of Li₂ Cp₂Fe.tmeda (2.0 g, 6.38 mmol) in 20 mL of THF, which was added via cannula. The reaction mixture was stirred at room temperature for one hour.

Measurement of an FTIR spectrum of the crude reaction mixture showed the presence of small and variable amounts of terminal butadiyne groups (2140 cm⁻¹). These groups were found to be undesirable as they slowly cross-link at room temperature giving an insoluble material. Thus, when these groups were observed, they could be coupled by addition of 2-3 drops of 1,7-bis(chlorotetramethyldisiloxyl)-m-carborane. The reaction was quenched by addition of cold aqueous NH₄Cl. After aqueous work-up and extraction with diethyl ether, the orange-brown organic polymer solution was dried over MgSO₄, filtered, and the solvent removed by water aspiration to give a viscous brown oil. The oil was further dried by heating for several hours in vacuo at 70° C. giving a tacky, brown solid. Yield: 5.52 g (83%).

Example 3

Synthesis of copolymer, Polymer III—A solution of THF (10 mL) and n-BuLi (10.2 mL of 2.5M) in a 250 mL Schlenk flask was cooled to −78° C. The solution was treated with hexachlorobutadiene (1.0 mL, 6.38 mmol) dropwise-over a period of 10 minutes. The cold bath was removed and the solution was stirred at room temperature giving a grey-brown slurry. After stirring for 2 hours at room temperature, the slurry of dilithiobutadiyne was transferred via cannula to a flask containing a THF solution (10 mL) of dichloromethylsilane (1.21 g, 12.77 mmol) at 0° C. The resulting mixture was stirred at room temperature for 30 minutes giving a brown solution. The solution was cooled to 0° C. and treated with a slurry of Li₂ Cp₂Fe.tmeda (2.0 g, 6.38 mmol) in 20 mL of THF, which was added via cannula. The reaction mixture was stirred at room temperature for one hour.

Measurement of an FTIR spectrum of the crude reaction mixture showed the presence of small and variable amounts of terminal butadiyne groups (2140 cm⁻¹). These groups were found to be undesirable as they slowly cross-link at room temperature giving an insoluble material. Thus, when these groups were observed, they could be coupled by addition of 2-3 drops of dimethylchlorosilane. The reaction was quenched by addition of cold aqueous NH₄Cl. After aqueous work-up and extraction with diethyl ether, the orange-brown organic polymer solution was dried over MgSO₄, filtered, and the solvent removed by water aspiration to give a viscous brown oil. The oil was further dried by heating for several hours in vacuo at 70° C. giving a tacky, brown solid, which was the copolymer, Polymer III. Yield: 1.67 g (82%).

Example 4

Synthesis of Polymer IV—A solution of THF (10 mL) and n-BuLi (10.2 mL of 2.5M) in a 250 mL Schlenk flask was cooled to −78° C. The solution was treated with hexachlorobutadiene (1.0 mL, 6.38 mmol) dropwise over a period of 10 minutes. The cold bath was removed and the solution was stirred at room temperature giving a grey-brown slurry. After stirring for 2 hours at room temperature, the slurry of dilithiobutadiyne was transferred via cannula to a flask containing a THF solution (10 mL) of 1,3-dichlorotetramethyldisiloxane (2.60 g, 12.77 mmol) at 0° C. The resulting mixture was stirred at room temperature for 30 minutes giving a brown solution. The solution was cooled to 0° C. and treated with a slurry of Li₂ Cp₂Fe.tmeda (2.0 g, 6.38 mmol) in 20 mL of THF, which was added via cannula. The reaction mixture was stirred at room temperature for one hour.

Measurement of an FTIR spectrum of the crude reaction mixture showed the presence of small and variable amounts of terminal butadiyne groups (2140 cm⁻¹). These groups were found to be undesirable as they slowly cross-link at room temperature giving an insoluble material. Thus, when these groups were observed, they could be coupled by addition of 2-3 drops of 1,3-dichlorotetramethyldisiloxane. The reaction was quenched by addition of cold aqueous NH₄Cl. After aqueous work-up and extraction with diethyl ether, the orange-brown organic polymer solution was dried over MgSO₄, filtered, and the solvent removed by water aspiration to give a viscous brown oil. The oil was further dried by heating for several hours in vacuo at 70° C. giving a viscous, brown solid, which was the copolymer, Polymer IV. Yield 2.65 g (84%).

Example 5

Synthesis of Polymer V—A solution of THF (10 ml) and n-BuLi (5.1 ml of 2.5 M, 12.75 mmol) at −78° C. was treated dropwise with hexachlorobutadiene (0.5 ml, 3.20 mmol) over 10 minutes. The reaction mixture was stirred at ambient temperature for 3 hours. The resulting dark grey slurry was transferred via cannula to a flask containing Me₂SiCl₂ (1.55 ml, 12.78 mmol) in THF (5 ml) at 0° C. The solution was stirred for thirty minutes at room temperature then cooled in an ice bath and treated with a slurry of (LiC₅H₄)₂Fe tmeda (3.0 g, 9.55 mmol) in 20 ml of THF. The resulting dark brown solution was stirred for one hour at room temperature and an infrared spectrum (NaCl) taken.

The IR spectrum of the crude reaction mixture showed a small peak at 2140 cm⁻¹ (terminal diacetylene groups). Several drops of Me₂SiCl₂ were added via syringe and the solution stirred for 20 minutes. The infrared spectrum was remeasured and additional drops of Me₂SiCl₂ were added if required. After the terminal butadiyne groups were no longer observed in the infrared spectrum, the solution was quenched with ice cold saturated NH₄Cl_((aq)) and purified by aqueous workup and extraction with diethyl ether. The Et₂O extracts were dried over MgSO₄, filtered, and the solvent removed leaving a viscous brown oil. Drying in vacuo at 50° C. for 8 hours gave a brown solid (the copolymer, Polymer V), which was soluble in THF, ether, and acetone but poorly soluble in hexane. Yield: 2.21 g (83%).

Example 6

Synthesis of the Thermoset of Polymer I—A 2.41 g sample of Polymer I was placed in an aluminum planchet. The sample was heated to 90° C. The sample was slowly placed under vacuum so as not to foam from the planchet. Evolution of volatiles had ceased after 20 minutes and the sample was held under full vacuum for 2 hours at 90° C. The sample was then cooled to room temperature and placed in a furnace under an argon atmosphere. The sample was then heated to 350° C. then cooled to 50° C. using the following heating sequence: Heated to 200° C. over 30 min.; isothermed at 200° C. for 120 min.; heated to 250° C. over 60 min.; isothermed at 250° C. for 180 min.; heated to 300° C. over 60 min.; isothermed at 300° C. for 180 min.; heated to 350° C. over 60 min; isothermed at 350° C. for 180 min.; cooled to 50° C. over 480 min. Upon removal from the planchet, the thermoset (2.33 g) was hard and visually void free.

Example 7

Synthesis of the Thermoset of Polymer II—A 2.23 g sample of Polymer II was placed in an aluminum planchet and heated to 80° C. The sample was slowly placed under vacuum so as not to foam from the planchet. Evolution of volatiles had ceased after 15 minutes and the sample was held under full vacuum, for one hour at 80° C. then heated an additional hour at 100° C. under full vacuum. The sample was then cooled to room temperature and placed in a furnace under an argon atmosphere. The sample was then heated to 350° C. then cooled to 50° C. using the following heating sequence: Heated to 200° C. over 30 min.; isothermed at 200° C. for 120 min.; heated to 250° C. over 60 min.; isothermed at 250° C. for 180 min.; heated to 300° C. over 60 min.; isothermed at 300° C. for 180 min.; heated to 350° C. over 60 min; isothermed at 350° C. for 180 min.; cooled to 50° C. over 480 min. The thermoset (2.14 g) was removed from the planchet and was elastomeric and visually void free.

Example 8

Synthesis of the Ceramic Obtained From Thermoset of Polymer I (Example 6)—A 1.93 g sample of the thermoset obtained from heat treatment of Polymer I to 350° C. (Example 6) was heated slowly to 1000° C. in a furnace using the following heating cycle: Heated to 300° C. from room temperature over 2 hours; isothermed at 300° C. for 2 hours; heated to 400° C. over 2 hours; isothermed at 400° C. for 3 hours; heated to 450° C. for one hour, isothermed at 450° C. for 3 hours; heated to 500 over one hour; isothermed at 500° C. for 3 hours; heated to 550° C. over one hour; isothermed at 550° C. for 3 hours; heated to 600° C. over one hour; isothermed at 600° C. for 3 hours; heated to 700° C. over 2 hours; isothermed at 700° C. for 2 hours; heated to 1000° C. over 3 hours. The sample was slowly cooled to 50° C. over 10 hours. The resulting ceramic (1.46 g) was hard and ferromagnetic as observed from its attraction to a bar magnet.

Example 9

Synthesis of Ceramic Obtained Directly from Polymer I (Example 1)—In the TGA, a 19.9 mg sample of Polymer I was placed in a ceramic crucible and heated from room temperature to 1000° C. under a nitrogen atmosphere at a rate of 10° C./min. After cooling to room temperature, a lustrous black ceramic remained (15.3 mg). The ceramic product was hard and ferromagnetic (attracted to a bar magnet).

Example 10

Synthesis of Ceramic Obtained Directly From Polymer 1 (Example 1)—In the TGA, an 18.9 mg sample of Polymer I was placed in a ceramic crucible and heated from room temperature to 1500° C. under a nitrogen atmosphere at a rate of 10° C./min. After cooling to room temperature, a lustrous black ceramic remained (14.2 mg). The ceramic product was hard and ferromagnetic (attracted to a bar magnet).

Example 11

Synthesis of Ceramic Obtained from Thermoset of Polymer II (Example 7)—A 1.89 g sample of the thermoset obtained from heat treatment of Polymer II to 350° C. (Example 7) was heated slowly to 1000° C. in a furnace using the following heating cycle: Heated to 300° C. from room temperature over 2 hours; isothermed at 300° C. for 2 hours; heated to 400° C. over 2 hours; isothermed at 400° C. for 3 hours; heated to 450 for one hour; isothermed at 450° C. for 3 hours; heated to 500° C. over one hour, isothermed at 500° C. for 3 hours; heated to 550° C. over one hour; isothermed at 550° C. for 3 hours; heated to 600° C. over one hour, isothermed at 600° C. for 3 hours; heated to 700° C. over 2 hours; isothermed at 700° C. for 2 hours; heated to 1000° C. over 3 hours. The sample was slowly cooled to 50° C. over 10 hours. The resulting ceramic (1.42 g) was hard and ferromagnetic as observed from its attraction to a bar magnet.

Example 12

Synthesis of Ceramic Obtained Directly From Polymer II (Example 2)—In the TGA, a 23.2 mg sample of Polymer II was placed in a ceramic crucible and heated from room temperature to 1500° C. under a nitrogen atmosphere at a rate of 10° C./min. After cooling to room temperature, a lustrous black ceramic remained (17.8 mg). The ceramic product was hard and ferromagnetic (attracted to a bar magnet).

Example 13

The ceramics made by pyrolysis of Polymer I and Polymer II were subjected to elemental analysis. The results are provided in Tables 1 and 2.

TABLE 1 Elemental Analysis of Polymer I and Ceramic Therefrom % C % H % Si % Fe Polymer 62.06 5.79 16.12 16.03 Ceramic (pyrolyzed at 1000° C.) 59.68 0.0 16.93 17.16

TABLE 2 Elemental Analysis of Polymer II and Ceramic Therefrom % C % H % Si % B % Fe Polymer 39.05 7.33 21.49 20.68 5.34 Ceramic (pyrolyzed at 1000° C.) 35.66 0.0 21.67 20.25 4.89

Example 13

Pyrolysis of Polymer I to 1000° C.—Ferrocenylene-siloxyl-diacetylene (24.62 mg) was weighed in a TGA pan and heated at 10° C. under a nitrogen atmosphere from room temperature to 1000° C. resulting in a char yield of 65%. The iron nanoparticle carbon composition was strongly attracted to a bar (permanent) magnet, indicating ferromagnetic behavior: X-ray diffraction study indicated the formation of carbon nanotubes and Fe₅Si₃ nanoparticle phase in the resulting pyrolytic composition.

Example 14

Pyrolysis of Polymer II to 1000° C.—Ferrocenylene-siloxyl-carboranyl-diacetylene (26.71 mg) was weighed in a TGA pan and heated at 10° C. under a nitrogen atmosphere from room temperature to 1000° C. resulting in a char yield of 83%. The iron nanoparticle carbon composition was attracted to a bar (permanent) magnet, indicating ferromagnetic behavior. X-ray diffraction study did not show the formation of carbon nanotubes. However, an unidentified metal nanoparticle phase was formed in the resulting pyrolytic composition. The precursor material (ferrocenylene-siloxyl-carboranyl-diacetylene) has iron, silicon, carbon, hydrogen, boron, and oxygen as elements in the linear polymer.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. It should also be noted that the entire specification and claims of the co-filed applications of the same title, now U.S. Pat. No. 5,986,032 and U.S. Pat. No. 5,844,052, are herein incorporated by reference for all purposes. 

What is claimed is:
 1. A transition metal-containing ceramic made by the process comprising the step of pyrolyzing an organometallic linear polymer containing at least one metallocenylene unit, at least one silyl or siloxyl unit, and at least one acetylene unit to form a ceramic; wherein the ceramic has a ceramic yield of at least about 75% by weight; and wherein the ceramic comprises metal nanoparticles.
 2. The transition metal-containing ceramic of claim 1, wherein the ceramic comprises at least about 55% by weight of total carbon and silicon.
 3. The ceramic of claim 1, wherein the pyrolysis comprises heating the linear polymer from room temperature to a temperature of at least 1000° C.
 4. The ceramic of claim 1, wherein the pyrolyzing is by heat treatment in excess of about 500° C.
 5. The ceramic of claim 1, wherein prior to pyrolyzing, fibers are incorporated into the linear organometallic polymer.
 6. A ceramic fiber comprising the ceramic of claim
 1. 7. A composite comprising the ceramic of claim 1 and at least one other material.
 8. The composite of claim 7, wherein said at least one other material is a reinforcing material.
 9. The ceramic of claim 1, wherein the pyrolysis is carried out in an inert atmosphere.
 10. The transition metal-containing ceramic of claim 1, wherein the ceramic further comprises carbon nanotubes.
 11. A transition metal-containing ceramic made by the process comprising the steps of: forming an organometallic linear polymer containing at least one metallocenylene, at least one silyl or siloxyl unit, and at least one acetylene unit; crosslinking said linear polymer through the acetylene units, thereby forming a thermoset; and pyrolyzing said thermoset to form a ceramic; wherein the ceramic has a ceramic yield of at least about 75% by weight; and wherein the ceramic comprises metal nanoparticles.
 12. The transition metal-containing ceramic of claim 11, wherein the ceramic comprises at least about 55% by weight of total carbon and silicon.
 13. The transition metal-containing ceramic of claim 11, wherein the thermoset comprises the formula:

represents a structure consisting of a plurality of crosslinked acetylenic moieties; x is greater than or equal to one; z is greater than or equal to one; w is greater than or equal to one; y is greater than or equal to one; a is greater than or equal to one; R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are the same or different and are selected from the group consisting of H, unsubstituted hydrocarbon moieties, substituted hydrocarbon moieties, and halogen; M is selected from the group consisting of Fe, Ru, Os, and combinations thereof; E is selected from the group consisting of

R¹³B; f is greater than or equal to zero; g is greater than or equal to one; h is greater than or equal to one; p is greater than or equal to zero; q is greater than or equal to zero; s is greater than or equal to zero and is greater than or equal to one when q is greater than or equal to one; t is greater than or equal to zero; k is an integer from 3 to 16; R⁹, R¹⁰, R¹¹, R¹² may be the same or different and wherein each is selected from the group consisting of H, unsubstituted hydrocarbon moieties, and substituted hydrocarbon moieties; and R¹³ is an unsubstituted or substituted hydrocarbon moiety.
 14. The transition metal-containing ceramic of claim 13, wherein a is 1, w is 1, y is 1, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are H, M is Fe, and E is Si(CH₃)₂—O—Si(CH₃)₂—CB₁₀H₁₀C—Si(CH₃)₂—O—Si(CH₃)₂.
 15. The transition metal-containing ceramic of claim 13, wherein a is 1, w is 1, y is 1, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are H, M is Fe, and E is Si(CH₃)H.
 16. The transition metal-containing ceramic of claim 13, wherein a is 1, w is 1, y is 1, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R8 are H, M is Fe, and E is Si(CH₃)₂.
 17. The transition metal-containing ceramic of claim 13, wherein a is 1, w is 1, y is 1, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are H, M is Fe, and E is Si(CH₃)₂—O—Si(CH₃)₂.
 18. The transition metal-containing ceramic of claim 13, wherein a is 1, w is 3, y is 1, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are H, M is Fe, and E is Si(CH₃)₂.
 19. The transition metal-containing ceramic of claim 11, wherein the ceramic further comprises carbon nanotubes.
 20. The ceramic of claim 11, wherein the pyrolysis is carried out in an inert atmosphere.
 21. The ceramic of claim 11, wherein the crosslinking is by photochemical or thermal processes.
 22. The ceramic of claim 11, wherein the thermoset was obtained by heat treatment of the organometallic linear polymer from room temperature to about 350° to 500° C.
 23. The ceramic of claim 11, wherein the pyrolyzing is by heat treatment in excess of about 500° C.
 24. The ceramic of claim 11, wherein prior to the crosslinking step, fibers are incorporated into the linear organometallic polymer.
 25. A transition metal-containing ceramic made by the process comprising the step of pyrolyzing an organometallic linear polymer containing at least one metallocenylene unit, at least one silyl or siloxyl unit, and at least one acetylene unit to form a ceramic; wherein the ceramic comprises metal nanoparticles.
 26. A transition metal-containing ceramic made by the process comprising the steps of: forming an organometallic linear polymer containing at least one metallocenylene, at least one silyl or siloxyl unit, and at least one acetylene unit; crosslinking said linear polymer through the acetylene units, thereby forming a thermoset; and pyrolyzing said thermoset to form a ceramic; wherein the ceramic comprises metal nanoparticles.
 27. The ceramic of claim 26, wherein the linear polymer is:


28. The ceramic of claim 26, wherein the linear polymer is:


29. The ceramic of claim 25, wherein the ceramic further comprises carbon nanotubes.
 30. The ceramic of claim 26, wherein the ceramic further comprises carbon nanotubes. 